THE REVISION KNEE ARTHROPLASTY
Porous metal metaphyseal cones for severe bone loss WHEN ONLY METAL WILL DO P. F. Lachiewicz, T. S. Watters From Duke University Medical Center, Durham, North Carolina, United States
Metaphyseal bone loss is common with revision total knee replacement (RTKR). Using the Anderson Orthopaedic Research Institute (AORI) classification, type 2-B and type 3 defects usually require large metal blocks, bulk structural allograft or highly porous metal cones. Tibial and femoral trabecular metal metaphyseal cones are a unique solution for large bone defects. These cones substitute for bone loss, improve metaphyseal fixation, help correct malalignment, restore the joint line and may permit use of a shorter stem. The technique for insertion involves sculpturing of the remaining bone with a high speed burr and rasp, followed by press-fit of the cone into the metaphysis. The fixation and osteoconductive properties of the porous cone outer surface allow ingrowth and encourage long-term biological fixation. The revision knee component is then cemented into the porous cone inner surface, which provides superior fixation compared with cementing into native but deficient metaphyseal bone. The advantages of the cone compared with allograft include: technical ease, biological fixation, no resorption, and possibly a lower risk of infection. The disadvantages include: difficult extraction and relatively short-term follow-up. Several studies using cones report promising short-term results for the reconstruction of large bone defects in RTKR. Cite this article: Bone Joint J 2014;96-B(11 Suppl A):118–21.
P. F. Lachiewicz, MD, Consulting Professor, Orthopaedic Surgery T. S. Watters, MD, Resident, Orthopaedic Surgery Duke University Medical Center, Department of Orthopaedic Surgery, 30 Duke Medicine Circle, Durham, North Carolina 27710, USA. Correspondence should be sent to Dr P. F. Lachiewicz; e-mail: [email protected] ©2014 The British Editorial Society of Bone & Joint Surgery doi:10.1302/0301-620X.96B11. 34197 $2.00 Bone Joint J 2014;96-B(11 Suppl A):118–21.
118
Metaphyseal bone loss is frequently encountered during revision total knee replacement (RTKR). The causes of this include component loosening or subsidence, periprosthetic osteolysis with or without loosening, chronic infection, and bony damage during component removal. The Anderson Orthopaedic Research Institute (AORI) classification of bone loss in revision knee arthroplasty is very helpful during pre-operative planning.1 Type 1 defects do not require metal augmentation of bone graft and should be managed with standard revision knee components, with or without stems. Type 2-A defects are usually managed with nonporous metal augments, wedges or blocks, with revision components and stems. With a type 2-B femur, there is extensive damage to both the medial and lateral femoral condyles and in a type 2-B tibia, there is similarly extensive damage to both the medial and lateral tibial plateaus. With such defects, there is not usually sufficient healthy bone for cement intrusion and consequent metaphyseal fixation with cement alone. With a type 3 defect of the distal femur or proximal tibia, there is usually almost complete loss of metaphyseal bone precluding cement fixation. Relying only on distal fixation in these circumstances usually leads to
loosening or stem fracture. Type 2-B and type 3 defects have conventionally been managed with a bulk structural allograft, but technical difficulties and the potential for allograft resorption leading to mechanical failure are of concern.2 Highly porous cones are a unique solution for large type 2-B and 3 defects of the distal femur and proximal tibia in RTKR. Their use and technique for insertion was initially described by Radnay and Scuderi3 in a small series of nine patients with a clinical follow-up of ten months.
Patients and methods Metal metaphyseal cones are fabricated of trabecular metal tantalum, a highly porous metal, with high strength, and high friction ‘microspikes’ which are impacted into the remaining bone shell of the distal femur or proximal tibia. This metal and its surface geometry facilitate osteoconduction with rapid bone ingrowth. One study of trabecular metal tibial components in primary TKR demonstrated secure fixation after five years follow-up using radiostereometric analysis (RSA).4 A randomised study reported that revisions using tibial tantalum cones had less migration using RSA, than revisions performed without such a cone.5 CCJR SUPPLEMENT TO THE BONE & JOINT JOURNAL
POROUS METAL METAPHYSEAL CONES FOR SEVERE BONE LOSS
119
Fig. 1 Trial trabecular metal cones: the upper 3 are femoral trials and the lower 3 are tibial trials.
Tantalum surfaces may also increase host white blood cell activation and lower bacterial adhesion, possibly decreasing the risk of infection.6,7 When initially introduced, tibial metaphyseal cones had limited numbers of shapes and sizes but now there are numerous options which are available in right or left sides, with ‘stepped’ cones to replace large asymmetrical defects and ‘full’ cones of various sizes to replace symmetrical defects (Fig. 1). There is also now a trial component with a ‘milling device’ to help preparation with a high-speed burr. When initially introduced, there were even more limited sizes and shapes for the distal femoral metaphyseal cones, an issue now also rectified. The function of metaphyseal cones are to substitute for lost or deficient tibial or femoral metaphyseal bone structure (Fig. 2). They improve cement fixation in the metaphysis so that there may be less reliance on distal stem fixation. With proper pre-operative planning, cones can help the surgeon correct malalignment of a failed implant and restore the proper joint line. In our experience, the use of metaphyseal cones permit the use of a shorter cemented tibial stem for fixation.8 The techniques for use of these metaphyseal cones first involve preparation of the remaining metaphyseal bone, or metaphyseal-diaphyseal junction with a high speed round or pencil-tip burr. There are now rasps which may assist with this preparation, but these require care to avoid fractures of the deficient residual bony shell. There is some ‘artistry’ in preparation of the bone to receive the porous cone. There are plastic trial components which also assist in the preparation of the metaphysis. After selection of the proper size and shape of the cone, it is then press-fitted with an impactor into the metaphyseal bone. VOL. 96-B, No. 11, NOVEMBER 2014
As the implant has more flexibility than the trial plastic component and along with the frictional properties of the cones, this provides for an excellent press-fit and bone ingrowth from the remaining viable bone. The interface of the cone and the remaining metaphyseal bone is then sealed with small crushed cancellous allograft chips usually mixed with a ‘bone putty’ material, such as demineralised bone matrix, which is available in multiple proprietary preparations from several manufacturers. The medullary canal is then occluded with a diaphyseal plastic cement plug and prepared for cement fixation. The revision tibial or femoral component, prepared with additional augments or wedges as necessary, is then cemented into the highly porous inner surface of the metaphyseal cone. This surface certainly has greater porosity than the damaged metaphyseal bone. The authors recommend the routine use of bone cement with antibiotic for RTKR. There are several advantages of porous metaphyseal cones when compared with the use of a bulk structural allograft for complex revisions. The technical aspects of bone preparation are easier with a cone than with a structural allograft, which requires more extensive preparation both to the allograft and its host sites. The cone facilitates biological fixation while the allograft relies on external healing and slow-host resorption. In a small randomised clinical study of 17 cones compared with 19 knees that underwent RTKR without a cone, the bone remodeling pattern was nearly the same between both groups with no significant difference in bone mineral density at two years.9 There may be a lower rate of infection with these cones compared with bulk allografts, but this has not been conclusively proven. As opposed to allograft bone, the metaphyseal cones will not have a possibility of late bone resorption and possible fracture.
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P. F. LACHIEWICZ, T. S. WATTERS
Table I. Outcomes of metaphyseal cones in revision total knee replacement Tibia/femur (implants)
Study (year) Meneghini et al (2008)10 Long and Scuderi (2009)11 Howard et al (2011)12 Lachiewicz et al (2012)13 Rao et al (2013)14 Schmitz et al (2013)15 Villanueva-Martinez et al (2013)16 Derome et al (2014)17
Pre-op class AORI*
Results
Number of knees
Tib Fem
2A/B
3
Reimplant Antibiotic for infection Mean follow-up bone (knees, %) (mths, range) cement?
15
15
0
7
8
5 (33)
34 (24 to 47)
YES
2 (13)
0 (0)
4 (27)
16
16
0
5
11
3 (19)
31 (24 to 38)
YES
2 (13)
0(0)
2(13)
24 27
0 24
24 9
NR§ 4
NR§ 29
7 (29) 13 (48)
33 (24 to 50) 40 (24 to 68)
NR§ YES
0 (0)¶ 1 (4)
0(0) 1 (4)
5 (21) 4 (15)
26 38 21
25 25 11
4 29 18
20 19 9
9 19 19
9 (35) 0 (0) 5 (24)
36 (24 to 49) 37 (32 to 48) 36 (6 to 55)
NR§ YES YES
2 (8) 0 (0) 2 (10)
0 (0) 1 (3) 0 (0)
2 (8) 2 (5) 2 (10)
29
17
16
NR§
NR§
7 (24)
33 (13 to 73)
YES
2 (7)
0 (0)
4 (14)
Infection (knees, %)
Loosening† (knees, %)
Reoperation‡ (knees, %)
* AORI, Anderson Orthopaedic Research Institute classification of metaphyseal defect † Denotes loosening of trabecular metal cone ‡ Denotes reoperation for any reason, including infection ¶ One patient in study population had positive cultures at staged re-implantation for infection in which cone was used and subsequently was treated with chronic suppressive antibiotics § NR, Not Reported (both studies not reporting breakdown of AORI classification state that all defects were either 2B or 3)
Fig. 2a
Fig. 2b
Pre-operative anteroposterior radiograph (a) showing a 58-year-old man with a loose cemented tibial component and severe metaphyseal bone loss. Five-year post-operative radiograph (b) showing reconstruction of the deficient tibial metaphysis with a large ‘stepped’ tibial cone and a cemented 30 mm stem extension.
There are several possible disadvantages of these cones compared with bulk structural allografts. These cones may only be used with the revision implants of the same manufacturer and they do not truly restore bone structure, but substitute for bone loss in order to permit repositioning of a revision component. With extensive bone ingrowth, these cones may be extremely difficult to remove if a deep infection occurs. Finally, as opposed to bulk structural allografts, there is only relatively short-term follow-up of revisions in which they were used.
Results There are only eight studies, to our knowledge, of the use of trabecular metal cones in RTKR (Table I).10-17 As expected with any new technique used only for severe bone deficiency, these studies have relatively small numbers of patients with follow-up times of only two to five years. Meneghini et al10 reported the first use of tibial cones in 15 patients who had an average of 3.5 prior knee surgeries. At mean follow-up of 34 months, all 15 cones had radiological evidence of osseointegration. Two patients had recurrence of infection, treated by debridement, liner exchange, and antibiotic suppression. Long and Scuderi11 reported similar results in 16 revision knees with tibial cones at a mean follow-up of 31 months. Two knees in this study that had reimplantation for infection had recurrent infection at three and eight months, respectively. Both were treated with resection of the implants. The two cones had bone ingrowth and required ‘significant work with a burr and osteotome’ to achieve removal, which is one disadvantage of these cones. Howard et al12 reported the first use of femoral cones in 24 revision knees with a mean follow-up of 33 months. These femoral cones had radiological osseointegration and there were no cone-related complications. Five patients had a re-operation for causes other than loosening. A combined series of tibial and femoral cones was reported by the senior author (PFL), which included 33 cones (nine femoral, 24 tibial) in 27 RTKRs with a mean follow-up of 40 months.13 Almost half of these knees had a staged re-implantation for infection. There was only one case of recurrent infection in a knee with both a femoral and tibial cone. All but one cone had osseointegration. One patient, with a hinged revision prosthesis and femoral cone, had gross loosening and was converted to a tumor prosthesis. CCJR SUPPLEMENT TO THE BONE & JOINT JOURNAL
POROUS METAL METAPHYSEAL CONES FOR SEVERE BONE LOSS
Rao et al14 reported the results of 29 cones in 26 knees with a mean follow-up of three years. Two of nine patients, with two-stage revision for infection, had recurrence of infection. One was treated with another two-stage revision and the other with long-term suppressive antibiotics. Schmitz et al15 reported the results of 25 tibial and 29 femoral cones in 38 RTKRs at 37 months follow-up. The indication for revision in all 38 was aseptic loosening. Two patients required re-operation: one for aseptic loosening of the femoral cone and component and the other had a loose tibial component but well-fixed tibial cone. Villanueva-Martinez et al16 reported the results of 11 tibial and 18 femoral cones in 21 knees at a mean follow-up of 36 months. There were two re-operations, both for recurrent infection. On the other hand, 20 knees had functioning implants and cone osseointegration. The main complication was intra-operative fracture in six patients; all related to cone insertion. There were two epicondyle fractures, three fractures of the anterior femoral diaphysis and one fracture of the proximal tibia. There were three cases of partial patellar tendon avulsion. This study emphasises the technical challenges of cone insertion into deficient metaphyseal bone. Derome et al17 recently reported the results of 33 cones (17 tibial, 16 femoral) in 29 revision knees. There was one intra-operative fracture. At a mean follow-up of 33 months, all cones had osseointegration, with two recurrent infections and two other re-operations unrelated to the cone. In conclusion, the relatively short-term clinical results of both tibial and femoral trabecular metal cones in revision knee arthroplasty are encouraging. Osseointegration, as determined by radiographs, occurs reliably both in knees revised for aseptic loosening and in knees with two-stage re-implantation for infection. In the eight studies with a combined total of 196 revision knees (233 cones), there were only two cases of aseptic loosening of the cone without bone ingrowth, both likely related to technical errors in cone preparation or cement technique. The main cause for failure or re-operation after two-stage revision for infection was not cone or component loosening, but recurrent infections. These highly porous metaphyseal cones are a promising method for the reconstruction of large contained or uncontained bone defects in revision knee arthroplasty. Longer follow-up is required to determine the durability of these constructs.
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We thank Mr. S. Perlman for help with the literature search. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. This paper is based on a study which was presented at the 30th Annual Winter 2013 Current Concepts in Joint Replacement® meeting held in Orlando, Florida, 11th – 14th December.
References 1. Engh GA, Ammeen DJ. Bone loss with revision total knee arthroplasty: defect classification and alternatives for reconstruction. Instr Course Lect 1999;48:167–175. 2. Haidukewych GJ, Hanssen A, Jones RD. Metaphyseal fixation in revision total knee arthroplasty: indications and techniques. J Am Acad Orthop Surg 2011;19:311– 318. 3. Radnay CS, Scuderi GR. Management of bone loss: augments, cones, offset stems. Clin Orthop Relat Res 2006;446:83–92. 4. Henricson A, Rösmark D, Nilsson KG. Trabecular metal tibia still stable at 5 years: an RSA study of 36 patients aged less than 60 years. Acta Orthop 2013;84:398–405. 5. Jensen CL, Petersen MM, Schrøder HM, Flivik G, Lund B. Revision total knee arthroplasty with the use of trabecular metal cones: a randomized radiostereometric analysis with 2 years of follow-up. J Arthroplasty 2012;27:1820–1826. 6. Schildhauer TA, Peter E, Muhr G, Koller M. Activation of human leukocytes on tantalum trabecular metal in comparison to commonly used orthopedic metal implant materials. J Biomed Mater Res A 2009;88:332–341. 7. Schildhauer TA, Robie B, Muhr G, Koller M. Bacterial adherence to tantalum versus commonly used orthopedic metallic implant materials. J Orthop Trauma 2006;20:476–484. 8. Lachiewicz PF, Soileau ES. A 30-mm Cemented Stem Extension Provides Adequate Fixation of the Tibial Component in Revision Knee Arthroplasty. Clin Orthop Relat Res 2014 Feb 20. [Epub ahead of print]. 9. Jensen CL, Petersen MM, Schrøder HM, Lund B. Bone mineral density changes of the proximal tibia after revision total knee arthroplasty. A randomised study with the use of porous tantalum metaphyseal cones. Int Orthop 2012;36:1857–1863. 10. Meneghini RM, Lewallen DG, Hanssen AD. Use of porous tantalum metaphyseal cones for severe tibial bone loss during revision total knee replacement. J Bone Joint Surg [Am] 2008;90-A:78–84. 11. Long WJ, Scuderi GR. Porous tantalum cones for large metaphyseal tibial defects in revision total knee arthroplasty: a minimum 2-year follow-up. J Arthroplasty 2009;24:1086–1092. 12. Howard JL, Kudera J, Lewallen DG, Hanssen AD. Early results of the use of tantalum femoral cones for revision total knee arthroplasty. J Bone Joint Surg [Am] 2011;93-A:478–484. 13. Lachiewicz PF, Bolognesi MP, Henderson RA, Soileau ES, Vail TP. Can tantalum cones provide fixation in complex revision knee arthroplasty? Clin Orthop Relat Res 2012;470:199–204. 14. Rao BM, Kamal TT, Vafaye J, Moss M. Tantalum cones for major osteolysis in revision knee replacement. Bone Joint J 2013;95-B:1069–1074. 15. Schmitz HC, Klauser W, Citak M, et al. Three-year follow up utilizing tantal cones in revision total knee arthroplasty. J Arthroplasty 2013;28:1556–1560. 16. Villanueva-Martínez M, De la Torre-Escudero B, Rojo-Manaute JM, RíosLuna A, Chana-Rodriguez F. Tantalum cones in revision total knee arthroplasty. A promising short-term result with 29 cones in 21 patients. J Arthroplasty 2013;28:988– 993. 17. Derome P, Sternheim A, Backstein D, Malo M. Treatment of large bone defects with trabecular metal cones in revision total knee arthroplasty: short term clinical and radiographic outcomes. J Arthroplasty 2014;29:122–126.
Porous metal metaphyseal cones for severe bone loss WHEN ONLY METAL WILL DO P. F. Lachiewicz, T. S. Watters From Duke University Medical Center, Durham, North Carolina, United States
Metaphyseal bone loss is common with revision total knee replacement (RTKR). Using the Anderson Orthopaedic Research Institute (AORI) classification, type 2-B and type 3 defects usually require large metal blocks, bulk structural allograft or highly porous metal cones. Tibial and femoral trabecular metal metaphyseal cones are a unique solution for large bone defects. These cones substitute for bone loss, improve metaphyseal fixation, help correct malalignment, restore the joint line and may permit use of a shorter stem. The technique for insertion involves sculpturing of the remaining bone with a high speed burr and rasp, followed by press-fit of the cone into the metaphysis. The fixation and osteoconductive properties of the porous cone outer surface allow ingrowth and encourage long-term biological fixation. The revision knee component is then cemented into the porous cone inner surface, which provides superior fixation compared with cementing into native but deficient metaphyseal bone. The advantages of the cone compared with allograft include: technical ease, biological fixation, no resorption, and possibly a lower risk of infection. The disadvantages include: difficult extraction and relatively short-term follow-up. Several studies using cones report promising short-term results for the reconstruction of large bone defects in RTKR. Cite this article: Bone Joint J 2014;96-B(11 Suppl A):118–21.
P. F. Lachiewicz, MD, Consulting Professor, Orthopaedic Surgery T. S. Watters, MD, Resident, Orthopaedic Surgery Duke University Medical Center, Department of Orthopaedic Surgery, 30 Duke Medicine Circle, Durham, North Carolina 27710, USA. Correspondence should be sent to Dr P. F. Lachiewicz; e-mail: [email protected] ©2014 The British Editorial Society of Bone & Joint Surgery doi:10.1302/0301-620X.96B11. 34197 $2.00 Bone Joint J 2014;96-B(11 Suppl A):118–21.
118
Metaphyseal bone loss is frequently encountered during revision total knee replacement (RTKR). The causes of this include component loosening or subsidence, periprosthetic osteolysis with or without loosening, chronic infection, and bony damage during component removal. The Anderson Orthopaedic Research Institute (AORI) classification of bone loss in revision knee arthroplasty is very helpful during pre-operative planning.1 Type 1 defects do not require metal augmentation of bone graft and should be managed with standard revision knee components, with or without stems. Type 2-A defects are usually managed with nonporous metal augments, wedges or blocks, with revision components and stems. With a type 2-B femur, there is extensive damage to both the medial and lateral femoral condyles and in a type 2-B tibia, there is similarly extensive damage to both the medial and lateral tibial plateaus. With such defects, there is not usually sufficient healthy bone for cement intrusion and consequent metaphyseal fixation with cement alone. With a type 3 defect of the distal femur or proximal tibia, there is usually almost complete loss of metaphyseal bone precluding cement fixation. Relying only on distal fixation in these circumstances usually leads to
loosening or stem fracture. Type 2-B and type 3 defects have conventionally been managed with a bulk structural allograft, but technical difficulties and the potential for allograft resorption leading to mechanical failure are of concern.2 Highly porous cones are a unique solution for large type 2-B and 3 defects of the distal femur and proximal tibia in RTKR. Their use and technique for insertion was initially described by Radnay and Scuderi3 in a small series of nine patients with a clinical follow-up of ten months.
Patients and methods Metal metaphyseal cones are fabricated of trabecular metal tantalum, a highly porous metal, with high strength, and high friction ‘microspikes’ which are impacted into the remaining bone shell of the distal femur or proximal tibia. This metal and its surface geometry facilitate osteoconduction with rapid bone ingrowth. One study of trabecular metal tibial components in primary TKR demonstrated secure fixation after five years follow-up using radiostereometric analysis (RSA).4 A randomised study reported that revisions using tibial tantalum cones had less migration using RSA, than revisions performed without such a cone.5 CCJR SUPPLEMENT TO THE BONE & JOINT JOURNAL
POROUS METAL METAPHYSEAL CONES FOR SEVERE BONE LOSS
119
Fig. 1 Trial trabecular metal cones: the upper 3 are femoral trials and the lower 3 are tibial trials.
Tantalum surfaces may also increase host white blood cell activation and lower bacterial adhesion, possibly decreasing the risk of infection.6,7 When initially introduced, tibial metaphyseal cones had limited numbers of shapes and sizes but now there are numerous options which are available in right or left sides, with ‘stepped’ cones to replace large asymmetrical defects and ‘full’ cones of various sizes to replace symmetrical defects (Fig. 1). There is also now a trial component with a ‘milling device’ to help preparation with a high-speed burr. When initially introduced, there were even more limited sizes and shapes for the distal femoral metaphyseal cones, an issue now also rectified. The function of metaphyseal cones are to substitute for lost or deficient tibial or femoral metaphyseal bone structure (Fig. 2). They improve cement fixation in the metaphysis so that there may be less reliance on distal stem fixation. With proper pre-operative planning, cones can help the surgeon correct malalignment of a failed implant and restore the proper joint line. In our experience, the use of metaphyseal cones permit the use of a shorter cemented tibial stem for fixation.8 The techniques for use of these metaphyseal cones first involve preparation of the remaining metaphyseal bone, or metaphyseal-diaphyseal junction with a high speed round or pencil-tip burr. There are now rasps which may assist with this preparation, but these require care to avoid fractures of the deficient residual bony shell. There is some ‘artistry’ in preparation of the bone to receive the porous cone. There are plastic trial components which also assist in the preparation of the metaphysis. After selection of the proper size and shape of the cone, it is then press-fitted with an impactor into the metaphyseal bone. VOL. 96-B, No. 11, NOVEMBER 2014
As the implant has more flexibility than the trial plastic component and along with the frictional properties of the cones, this provides for an excellent press-fit and bone ingrowth from the remaining viable bone. The interface of the cone and the remaining metaphyseal bone is then sealed with small crushed cancellous allograft chips usually mixed with a ‘bone putty’ material, such as demineralised bone matrix, which is available in multiple proprietary preparations from several manufacturers. The medullary canal is then occluded with a diaphyseal plastic cement plug and prepared for cement fixation. The revision tibial or femoral component, prepared with additional augments or wedges as necessary, is then cemented into the highly porous inner surface of the metaphyseal cone. This surface certainly has greater porosity than the damaged metaphyseal bone. The authors recommend the routine use of bone cement with antibiotic for RTKR. There are several advantages of porous metaphyseal cones when compared with the use of a bulk structural allograft for complex revisions. The technical aspects of bone preparation are easier with a cone than with a structural allograft, which requires more extensive preparation both to the allograft and its host sites. The cone facilitates biological fixation while the allograft relies on external healing and slow-host resorption. In a small randomised clinical study of 17 cones compared with 19 knees that underwent RTKR without a cone, the bone remodeling pattern was nearly the same between both groups with no significant difference in bone mineral density at two years.9 There may be a lower rate of infection with these cones compared with bulk allografts, but this has not been conclusively proven. As opposed to allograft bone, the metaphyseal cones will not have a possibility of late bone resorption and possible fracture.
120
P. F. LACHIEWICZ, T. S. WATTERS
Table I. Outcomes of metaphyseal cones in revision total knee replacement Tibia/femur (implants)
Study (year) Meneghini et al (2008)10 Long and Scuderi (2009)11 Howard et al (2011)12 Lachiewicz et al (2012)13 Rao et al (2013)14 Schmitz et al (2013)15 Villanueva-Martinez et al (2013)16 Derome et al (2014)17
Pre-op class AORI*
Results
Number of knees
Tib Fem
2A/B
3
Reimplant Antibiotic for infection Mean follow-up bone (knees, %) (mths, range) cement?
15
15
0
7
8
5 (33)
34 (24 to 47)
YES
2 (13)
0 (0)
4 (27)
16
16
0
5
11
3 (19)
31 (24 to 38)
YES
2 (13)
0(0)
2(13)
24 27
0 24
24 9
NR§ 4
NR§ 29
7 (29) 13 (48)
33 (24 to 50) 40 (24 to 68)
NR§ YES
0 (0)¶ 1 (4)
0(0) 1 (4)
5 (21) 4 (15)
26 38 21
25 25 11
4 29 18
20 19 9
9 19 19
9 (35) 0 (0) 5 (24)
36 (24 to 49) 37 (32 to 48) 36 (6 to 55)
NR§ YES YES
2 (8) 0 (0) 2 (10)
0 (0) 1 (3) 0 (0)
2 (8) 2 (5) 2 (10)
29
17
16
NR§
NR§
7 (24)
33 (13 to 73)
YES
2 (7)
0 (0)
4 (14)
Infection (knees, %)
Loosening† (knees, %)
Reoperation‡ (knees, %)
* AORI, Anderson Orthopaedic Research Institute classification of metaphyseal defect † Denotes loosening of trabecular metal cone ‡ Denotes reoperation for any reason, including infection ¶ One patient in study population had positive cultures at staged re-implantation for infection in which cone was used and subsequently was treated with chronic suppressive antibiotics § NR, Not Reported (both studies not reporting breakdown of AORI classification state that all defects were either 2B or 3)
Fig. 2a
Fig. 2b
Pre-operative anteroposterior radiograph (a) showing a 58-year-old man with a loose cemented tibial component and severe metaphyseal bone loss. Five-year post-operative radiograph (b) showing reconstruction of the deficient tibial metaphysis with a large ‘stepped’ tibial cone and a cemented 30 mm stem extension.
There are several possible disadvantages of these cones compared with bulk structural allografts. These cones may only be used with the revision implants of the same manufacturer and they do not truly restore bone structure, but substitute for bone loss in order to permit repositioning of a revision component. With extensive bone ingrowth, these cones may be extremely difficult to remove if a deep infection occurs. Finally, as opposed to bulk structural allografts, there is only relatively short-term follow-up of revisions in which they were used.
Results There are only eight studies, to our knowledge, of the use of trabecular metal cones in RTKR (Table I).10-17 As expected with any new technique used only for severe bone deficiency, these studies have relatively small numbers of patients with follow-up times of only two to five years. Meneghini et al10 reported the first use of tibial cones in 15 patients who had an average of 3.5 prior knee surgeries. At mean follow-up of 34 months, all 15 cones had radiological evidence of osseointegration. Two patients had recurrence of infection, treated by debridement, liner exchange, and antibiotic suppression. Long and Scuderi11 reported similar results in 16 revision knees with tibial cones at a mean follow-up of 31 months. Two knees in this study that had reimplantation for infection had recurrent infection at three and eight months, respectively. Both were treated with resection of the implants. The two cones had bone ingrowth and required ‘significant work with a burr and osteotome’ to achieve removal, which is one disadvantage of these cones. Howard et al12 reported the first use of femoral cones in 24 revision knees with a mean follow-up of 33 months. These femoral cones had radiological osseointegration and there were no cone-related complications. Five patients had a re-operation for causes other than loosening. A combined series of tibial and femoral cones was reported by the senior author (PFL), which included 33 cones (nine femoral, 24 tibial) in 27 RTKRs with a mean follow-up of 40 months.13 Almost half of these knees had a staged re-implantation for infection. There was only one case of recurrent infection in a knee with both a femoral and tibial cone. All but one cone had osseointegration. One patient, with a hinged revision prosthesis and femoral cone, had gross loosening and was converted to a tumor prosthesis. CCJR SUPPLEMENT TO THE BONE & JOINT JOURNAL
POROUS METAL METAPHYSEAL CONES FOR SEVERE BONE LOSS
Rao et al14 reported the results of 29 cones in 26 knees with a mean follow-up of three years. Two of nine patients, with two-stage revision for infection, had recurrence of infection. One was treated with another two-stage revision and the other with long-term suppressive antibiotics. Schmitz et al15 reported the results of 25 tibial and 29 femoral cones in 38 RTKRs at 37 months follow-up. The indication for revision in all 38 was aseptic loosening. Two patients required re-operation: one for aseptic loosening of the femoral cone and component and the other had a loose tibial component but well-fixed tibial cone. Villanueva-Martinez et al16 reported the results of 11 tibial and 18 femoral cones in 21 knees at a mean follow-up of 36 months. There were two re-operations, both for recurrent infection. On the other hand, 20 knees had functioning implants and cone osseointegration. The main complication was intra-operative fracture in six patients; all related to cone insertion. There were two epicondyle fractures, three fractures of the anterior femoral diaphysis and one fracture of the proximal tibia. There were three cases of partial patellar tendon avulsion. This study emphasises the technical challenges of cone insertion into deficient metaphyseal bone. Derome et al17 recently reported the results of 33 cones (17 tibial, 16 femoral) in 29 revision knees. There was one intra-operative fracture. At a mean follow-up of 33 months, all cones had osseointegration, with two recurrent infections and two other re-operations unrelated to the cone. In conclusion, the relatively short-term clinical results of both tibial and femoral trabecular metal cones in revision knee arthroplasty are encouraging. Osseointegration, as determined by radiographs, occurs reliably both in knees revised for aseptic loosening and in knees with two-stage re-implantation for infection. In the eight studies with a combined total of 196 revision knees (233 cones), there were only two cases of aseptic loosening of the cone without bone ingrowth, both likely related to technical errors in cone preparation or cement technique. The main cause for failure or re-operation after two-stage revision for infection was not cone or component loosening, but recurrent infections. These highly porous metaphyseal cones are a promising method for the reconstruction of large contained or uncontained bone defects in revision knee arthroplasty. Longer follow-up is required to determine the durability of these constructs.
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We thank Mr. S. Perlman for help with the literature search. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. This paper is based on a study which was presented at the 30th Annual Winter 2013 Current Concepts in Joint Replacement® meeting held in Orlando, Florida, 11th – 14th December.
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